Make advanced reasoning selection explicit in the TUI (#32746)

## Why

`Max` and `Ultra` consume usage limits faster than standard reasoning levels, so they should not be selected accidentally while navigating the normal effort scale.

## What changed

- Move `Max` and `Ultra` behind a `More reasoning…` entry with a dedicated warning and descriptions.
- Keep the reasoning shortcuts from silently increasing into advanced efforts.
- Apply `Ultra` to the active conversation without changing defaults for new threads, while preserving it across mode switches and thread resumes.
- Record applied thread settings in thread metadata, including explicit clearing of reasoning effort, so resumed threads restore their latest model settings unless the user supplied an override.

## Testing

- Add TUI coverage for the advanced picker, shortcuts, Plan mode, configuration defaults, and resumed conversations.
- Add app-server and thread-store coverage for persisting, clearing, and restoring model and reasoning settings.

GitOrigin-RevId: 6708c7c2e8d38f491bf63000ea34f83476afdfe6

codex-rs/app-server/src/request_processors/thread_processor.rs

@@ -2788,15 +2788,18 @@ impl ThreadRequestProcessor {
             developer_instructions,
             personality,
         );
-        self.load_and_apply_persisted_resume_metadata(
-            &thread_history,
-            &mut request_overrides,
-            &mut typesafe_overrides,
-        )
-        .await;
+        let has_explicit_model_resume_override =
+            has_model_resume_override(request_overrides.as_ref(), &typesafe_overrides);
+        let persisted_metadata = self
+            .load_and_apply_persisted_resume_metadata(
+                &thread_history,
+                &mut request_overrides,
+                &mut typesafe_overrides,
+            )
+            .await;
 
         // Derive a Config using the same logic as new conversation, honoring overrides if provided.
-        let config = match self
+        let mut config = match self
             .config_manager
             .load_for_cwd(request_overrides, typesafe_overrides, history_cwd)
             .await
@@ -2808,6 +2811,13 @@ impl ThreadRequestProcessor {
                 return Ok(());
             }
         };
+        if !has_explicit_model_resume_override
+            && persisted_metadata
+                .as_ref()
+                .is_some_and(|metadata| metadata.reasoning_effort.is_none())
+        {
+            config.model_reasoning_effort = None;
+        }
 
         let response_history = thread_history.clone();